1. Field of the Invention
The present invention relates to a semiconductor device and a method for manufacturing the same wherein a lid wafer having a recess is joined to a body wafer having a circuit pattern.
2. Background Art
In recent years, applications using millimeter wave band, such as 60 GHz-band WPAN (Wireless Personal Area Network) and 76 GHz-band on-board millimeter wave radars, have been increased. These applications need semiconductor devices having high gain in millimeter wave band. Although a semiconductor device wherein semiconductor chips are sealed with a mold can reduce manufacturing costs, parasitic capacitance increases and the performance of the device deteriorates. In particular, the quantity of deterioration is marked in the millimeter wave band. In addition, the moisture resistance is not sufficiently maintained. Therefore, a semiconductor device wherein a lid wafer having a recess is joined to a body wafer having a circuit pattern formed has been proposed. Thereby, the circuit pattern is air-tightly sealed to improve moisture resistance, and gain lowering by parasitic capacitance can be repressed.
Furthermore, there is a problem wherein if a part of signals are fed back in a device, undesired oscillation is generated in the amplifier, or oscillation signals become misaligned in the oscillator. Particularly, since millimeter waves have short wavelength, self interference cannot be ignored. Therefore, a semiconductor device wherein an electromagnetic shield is provided on the inner surface of a lid wafer for covering the circuit pattern has been proposed (for example, refer to FIG. 11 in Japanese Patent Laid-Open No. 2005-57136).
Further, a semiconductor device wherein a circuit pattern is provided on the inner surface of a lid wafer and is connected to the circuit pattern of a body wafer has also been proposed (for example, refer to FIG. 10 in Japanese Patent Laid-Open No. 2005-57136). Thereby, the chip size can be reduced.